Emerging trends in sperm selection: enhancing success rates in assisted reproduction

This comprehensive review explores the evolving landscape of sperm selection techniques within the realm of Assisted Reproductive Technology (ART). Our analysis delves into a range of methods from traditional approaches like density gradient centrifugation to advanced techniques such as Magnetic-Activated Cell Sorting (MACS) and Intracytoplasmic Morphologically Selected Sperm Injection (IMSI). We critically assess the efficacy of these methods in terms of sperm motility, morphology, DNA integrity, and other functional attributes, providing a detailed comparison of their clinical outcomes. We highlight the transition from conventional sperm selection methods, which primarily focus on physical characteristics, to more sophisticated techniques that offer a comprehensive evaluation of sperm molecular properties. This shift not only promises enhanced prediction of fertilization success but also has significant implications for improving embryo quality and increasing the chances of live birth. By synthesizing various studies and research papers, we present an in-depth analysis of the predictability of different sperm selection procedures in ART. The review also discusses the clinical applicability of these methods, emphasizing their potential in shaping the future of assisted reproduction. Our findings suggest that the integration of advanced sperm selection strategies in ART could lead to more cost-effective treatments with reduced duration and higher success rates. This review aims to provide clinicians and researchers in reproductive medicine with comprehensive insights into the current state and future prospects of sperm selection technologies in ART.

The Use of Non-Apoptotic Sperm Selected by Magnetic Activated Cell Sorting (MACS) to Enhance Reproductive Outcomes: What the Evidence Says

Sperm selection of the most competent sperm is a promising way to enhance reproductive outcomes. Apoptosis is the programmed cell death process to maintain tissue homeostasis, and MACS sperm selection of non-apoptotic cells enables the removal of apoptotic sperm from an ejaculate, thus leaving the non-apoptotic available to be microinjected, but given the associated costs of adding these sperm selection steps to the routine practice, there is a need for a careful examination of the literature available to answer questions such as who can benefit from this MACS, how significant this improvement is, and how robust the evidence and data available supporting this choice are. Thus, the aim of this narrative review was to objectively evaluate the available evidence regarding the potential benefits of the use of MACS. From the literature, there are controversial results since its implementation as an in vitro fertilization add-on, and this may be explained in part by the low quality of the evidence available, wrong designs, or even inadequate statistical analyses. We concluded that the benefits of adding MACS are unclear, and further methodologically sound research on specific populations is much needed before offering it clinically.

Semen processing using magnetic-activated cell sorting before ICSI is deemed safe for obstetric and perinatal outcomes: a retrospective multicentre study

RESEARCH QUESTION

Is magnetic-activated cell sorting (MACS) a safe semen sample processing technique for newborns and mothers when used for semen processing prior to intracytoplasmic sperm injection (ICSI) cycles?

DESIGN

This retrospective multicentre cohort study involved patients undergoing ICSI cycles with either donor or autologous oocytes from January 2008 to February 2020. They were divided into two groups: those who underwent standard semen preparation (reference group) and those who had an added MACS procedure (MACS group). A total of 25,356 deliveries were assessed in the case of cycles using donor oocytes, and 19,703 deliveries from cycles using autologous oocytes. Of these, 20,439 and 15,917, respectively, were singleton deliveries. Obstetric and perinatal outcomes were retrospectively assessed. All means, rates and incidences were computed per live newborn in each study group.

RESULTS

There were no significant differences between the main obstetric and perinatal morbidities affecting the mothers' and newborns' well-being between groups using either donated or autologous oocytes. There was a significant increase in the incidence of gestational anaemia in both subpopulations (donor oocytes P = 0.01; autologous oocytes P < 0.001). However, this incidence was within the estimated prevalence for gestational anaemia in the general population. There was a statistically significant decrease in preterm (P = 0.02) and very preterm (P = 0.01) birth rates in the MACS group in cycles using donor oocytes.

CONCLUSIONS

The use of MACS during semen preparation before ICSI using either donor or autologous oocytes appears to be safe for the mothers' and newborns' well-being during pregnancy and birth. Nevertheless, a close follow-up of these parameters in the future is advised, especially concerning anaemia, in order to detect even smaller effect sizes.

Advanced Sperm Selection Strategies as a Treatment for Infertile Couples: A Systematic Review

Assisted reproductive technology (ART) is an essential tool to overcome infertility, and is a worldwide disease that affects millions of couples at reproductive age. Sperm selection is a crucial step in ART treatment, as it ensures the use of the highest quality sperm for fertilization, thus increasing the chances of a positive outcome. In recent years, advanced sperm selection strategies for ART have been developed with the aim of mimicking the physiological sperm selection that occurs in the female genital tract. This systematic review sought to evaluate whether advanced sperm selection techniques could improve ART outcomes and sperm quality/functionality parameters compared to traditional sperm selection methods (swim-up or density gradients) in infertile couples. According to preferred reporting items for systematic reviews and meta-analyses (PRISMA guidelines), the inclusion and exclusion criteria were defined in a PICOS (population, intervention, comparator, outcome, study) table. A systematic search of the available literature published in MEDLINE-PubMed until December 2021 was subsequently conducted. Although 4237 articles were recorded after an initial search, only 47 studies were finally included. Most reports (30/47; 63.8%) revealed an improvement in ART outcomes after conducting advanced vs. traditional sperm selection methods. Among those that also assessed sperm quality/functionality parameters (12/47), there was a consensus (10/12; 83.3%) about the beneficial effect of advanced sperm selection methods on these variables. In conclusion, the application of advanced sperm selection methods improves ART outcomes. In spite of this, as no differences in the reproductive efficiency between advanced methods has been reported, none can be pointed out as a gold standard to be conducted routinely. Further research addressing whether the efficiency of each method relies on the etiology of infertility is warranted.

Cumulative live birth rates in donor oocyte ICSI cycles are not improved by magnetic-activated cell sorting sperm selection

RESEARCH QUESTION

Does magnetic-activated cell sorting (MACS) for sperm selection increase cumulative live birth rates (CLBR) or improve clinical parameters of reproductive success in couples undergoing intracytoplasmic sperm injection (ICSI) with donor oocytes?

DESIGN

Retrospective multicentre observational study including data compiled from unselected couples who underwent ICSI cycles with donated oocytes in 15 Spanish IVIRMA fertility clinics (January 2008 to February 2020). Patients were divided into reference (standard semen processing, n = 40,157) and MACS (additional sperm selection step by MACS, n = 1,240) groups. CLBR were plotted on Kaplan-Meier curves and compared using the Mantel-Cox test. Proportions were compared with a generalized estimating equation model, and results were adjusted to clinically relevant variables.

RESULTS

The MACS group showed a 27.1% CLBR after one embryo was transferred and 81.6% after four; the reference group had CLBR of 19.6% and 78.5%, respectively. CLBR in the MACS group was 4.2% after five oocytes were used and 75.5% after 15; for the reference group, CLBR were 7.8% and 78.3%, respectively. Kaplan-Meier curves showed statistically significant differences in CLBR per number of embryos transferred and per number of donated metaphase II oocytes between the two groups (both P < 0.0001), but not for CLBR per embryo transfer. No significant differences between groups were found for classical clinical outcomes such as pregnancy and live birth rates per embryo transfer.

CONCLUSIONS

Although MACS sperm selection slightly increased the CLBR per embryo transferred compared with the reference group, this change was not clinically meaningful. MACS should not be recommended indiscriminately to all infertile patients undergoing ICSI with donated oocytes as a sperm processing add-on.

Sperm Selection by Magnetic-Activated Cell Sorting before Microinjection of Autologous Oocytes Increases Cumulative Live Birth Rates with Limited Clinical Impact: A Retrospective Study in Unselected Males

Simple Summary

Many couples attending infertility clinics still need to repeat treatments and undergo several failed attempts before achieving a healthy newborn, which leaves room for improvement in the techniques we currently use in the clinic. Among the different procedures susceptible to improvement, the selection of the most adequate sperm to be injected inside the egg is crucial to the cycle’s success. Magnetic-activated cell sorting (MACS) is a technique that removes physiologically abnormal sperm that have started a programmed cell death (apoptotic) process from a semen sample. However, it is not recommended to all patients because there is no agreement between the published literature on whether it improves reproductive outcomes. This study used data from all intracytoplasmic sperm injection cycles performed using the patient’s own oocytes in our clinics from January 2008 to February 2020. Our findings support that MACS should not be recommended to all infertile couples, since there was no significant difference in results compared to treatments in which MACS was not used. This study provides clinicians and patients with more accurate information on how MACS will impact their chances of pregnancy, and it will lead to studies focused on specific populations to which the technique can be particularly helpful.

Abstract

The application of MACS non-apoptotic sperm selection in infertility clinics is controversial since the published literature does not agree on its effect on reproductive outcomes. Therefore, it is not part of the routine clinical practice. Classical measures of reproductive success (pregnancy or live birth rates per ovarian stimulation) introduce a bias in the evaluation of a technique’s effect, since only the best embryo is transferred. This retrospective, multicenter, observational study evaluated the impact of MACS on reproductive outcomes, measuring results in classical parameters and cumulative live birth rates (CLBR). Data from ICSI cycles using autologous oocyte in Spanish IVIRMA fertility clinics from January 2008 to February 2020 were divided into two groups according to their semen processing: standard practice (reference: 46,807 patients) versus an added MACS sperm selection (1779 patients). Only when measured as CLBR per embryo transferred and per MII oocyte used was the difference between groups statistically significant. There were no significant differences between MACS and reference groups on pregnancy and live birth rates. In conclusion, results suggest that non-apoptotic sperm selection by MACS on unselected males prior to ICSI with autologous oocytes has limited clinical impact, showing a subtle increase in CLBR per embryo transferred.

The Effects of In Vitro Maturation Technique on The Expression of Genes Involved in Embryonic Genome Activation of Human Embryos

Objective

In vitro maturation technique (IVM) is shown to have an effect on full maturation of immature oocytes and the subsequent embryo development. Embryonic genome activation (EGA) is considered as a crucial and the first process after fertilization. EGA failure leads to embryo arrest and possible implantation failure. This study aimed to determine the role of IVM in EGA-related genes expression in human embryo originated from immature oocytes and recovered from women receiving gonadotrophin treatment for assisted reproduction.

Materials and Methods

In this experimental study, germinal vesicle (GV) oocytes were cultured in vitro. After intracytoplasmic sperm injection of the oocytes, fertilization, cleavage and embryo quality score were assessed in vitro and in vivo. After 3-4 days, a single blastomere was biopsied from the embryos and then frozen. Afterwards, the expression of EGA-related genes in embryos was assayed using quantitative reverse transcriptase-polymerase chain reaction (PCR).

Results

The in vitro study showed reduced quality of embryos. No significant difference was found between embryo quality scores for the two groups (P=0.754). The in vitro group exhibited a relatively reduced expression of the EGA- related genes, when compared to the in vivo group (all of them showed P=0.0001).

Conclusion

Although displaying the normal morphology, the IVM process appeared to have a negative influence on developmental gene expression levels of human preimplanted embryos. Based on our results, the embryo normal morphology cannot be considered as an ideal scale for the successful growth of embryo at implantation and downstream processes.

Does sperm DNA fragmentation affect the developmental potential and the incidence of apoptosis following blastomere biopsy?

Common methods employed in assisted reproduction technology (ART) include intracytoplasmic sperm injection (ICSI) with an unspecified level of sperm DNA fragmentation (SDF) and preimplantation genetic diagnosis (PGD). The aim of this study was to investigate the impact of SDF on human preimplantation embryo development and the incidence of apoptosis following a single blastomere biopsy. Using sperm chromatin dispersion (SCD) to assess SDF, a total of 20 processed semen samples were categorized into two groups; group I: SDF ≤30% and group II: SDF >30%. After ICSI, fertilization, cleavage, and embryo quality score were assessed. A single blastomere was biopsied from day 3 embryos and development was monitored on day 4. The frequency of apoptosis in biopsied embryos was assayed by TUNEL and the level of BCL-2, BAX, hsa-mir-15a, and hsa-mir-16-1 were assessed by quantitative real-time polymerase chain reaction (qRT-PCR). SCD was found to be negatively correlated with sperm motility and normal form spermatozoa (p < 0.05). The rate of fertilization, cleavage, and embryo quality score were not significantly different between the two groups (all p > 0.05). SDF >30% had no negative effect on potential development and did not increase the proportion of apoptotic cells and the level of apoptosis-related genes and microRNAs (miRNAs) in group II vs. group I (p > 0.05). It appears that at the levels assessed paternal genome damage had little if any negative effect on preimplantaton embryo development and apoptosis following single blastomere biopsy. This may reflect the selection of morphologically normal sperm for ICSI and the repair capacity of the oocyte.

Acquiring Kupffer cells in mice using a MACS-based method

OBJECTIVE

This study sought to establish a new method to isolate Kupffer cells (KCs) by magnetic activated cell sorting (MACS).

METHODS

Nonparenchymal cells were acquired from C57BL/6 mice livers by a perfusion system in vivo and then stained with F4/80(+) fluorescein isothiocyanate and CD11c(-) phycoerythrin antibodies. After incubating with immunomagnetic beads, F4/80(+)CD11c(-) KCs were obtained by MACS selection. The purity was evaluated by flow cytometry, and the morphological features and vitality were analyzed in in vitro cultures.

RESULTS

Compared with traditional methods, acquiring KCs by MACS was characterized by economy, efficiency, and high purity. The F4/80(+)CD11c(-) KCs cultured in vitro also showed the typical adherent shape and excellent phagocytic ability.

CONCLUSIONS

With the 2-step method using immunomagnetic beads, we provide a new method by which KCs can be obtained from mouse liver with high purity and distinct phenotype of F4/80(+) CD.

DNA fragmentation in human sperm after magnetic-activated cell sorting

PURPOSE

As fertilization with unselected apoptotic spermatozoa may contribute to failures in assisted reproductive techniques, it has become essential to remove this type of sperm in order to increase the success rates. Magnetic-activated cell sorting (MACS) is a sperm preparation technique that isolates non-apoptotic spermatozoa based on the expression of phosphatidylserine in the membrane of apoptotic sperm. Therefore, we aimed to evaluate whether there was a significant decrease in sperm DNA fragmentation (sDNAfrag) and verify which protocol was the most efficient.

METHODS

Hundred semen samples were allocated into five distinct groups and processed according to a combination of MACS with density gradient centrifugation (DGC) and swim-up (SU) techniques. Sperm DNA fragmentation was evaluated by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay.

RESULTS

Groups DGC-SU (73.4 %), DGC-MACS-SU (78.9 %), DGC-SU-MACS (53.8 %) and MACS-SU (73.5 %) presented a significant decrease in sDNAfrag but the highest reduction rate was obtained with MACS-DGC-SU (83.3 %). The later was also negatively correlated with sperm vitality, membrane integrity and progressive motility. Additionally, teratozoospermic patients presented a tendency to have lower sDNAfrag reduction rates than asthenozoospermic and asthenoteratozoospermic patients.

CONCLUSIONS

Based on the results, MACS showed potential to optimize the sDNAfrag reduction rate, when applied to raw semen, before DGC and SU, especially in samples with low values of progressive motility, vitality and hypoosmotic swelling test.

Apoptosis-like events and in vitro fertilization capacity of sex-sorted bovine sperm

This study utilized three staining assays (Annexin V, mitochondrial membrane potential (JC-1) and TUNEL) for flow cytometric analysis of apoptosis in sex-sorted sperm from four different bulls (A, B, C and D). Correlations between sperm quality and IVF efficiency were then assessed to determine which assay provided the best prediction of IVF efficiency. The results of the Annexin V assays, as well as measures of viable sperm, early apoptosis, necrotic sperm and mitochondrial membrane potential (∆ψm) showed that the sex-sorted sperm collected from bull A significantly differed from those of the other three bulls (p < 0.05). In addition, the levels of DNA fragmentation in sex-sorted sperm from bull A were significantly lower than those from bulls B and C (p < 0.05). The percentage of cells reaching the cleavage and blastocyst stages in sex-sorted sperm from bull A were significantly greater than those from the other bulls (p < 0.05). A significant positive correlation was observed between viable sperm and the percentage of cells at the cleavage or blastocyst stages (p < 0.05). In contrast, a negative correlation was found between early apoptotic sperm and the percentage of cells at the cleavage or blastocyst stages (p < 0.05). In conclusion, these results indicated that the Annexin V assay was the most reliable technique for the prediction of the IVF success of sex-sorted bovine sperm.